Does Blood Flow Restriction Enhance Exercise-mediated Changes In The Plantar Flexors?

Abstract

The plantar flexor muscle group readily atrophies when exposed to an unloaded environment (i.e. microgravity). There is evidence that the plantar flexors are also resistant to exercise stimuli when compared to other musculature. A rather novel training method called Kaatsu, or blood flow restriction (BFR) training, may potentially provide a substantial resistance training stimulus to the plantar flexors. PURPOSE: To determine if there are differences in strength and body composition after five weeks of training utilizing fatiguing protocols with or without BFR. METHODS: Seven physically inactive subjects (6 male, 1 female) engaged in five weeks of resistance training for the plantar flexors. Each leg was randomly assigned to one of three protocols: 1) high intensity (HIT), 2) low intensity (LIT), or 3) low intensity with blood flow restriction (BFR). Exercise sessions consisted of three sets to fatigue with 1.5 minutes of rest between sets. Each repetition consisted of a maximal shortening contraction followed by a controlled lengthening contraction regulated audibly by a metronome. Exercise was conducted unilaterally on hack squat equipment. Sets were terminated when 80% of full ROM was not obtained for two consecutive repetitions. For BFR, pressure was applied just superior to the proximal patella at 1.3 x systolic blood pressure and was maintained through the duration of the protocol. RESULTS: No significant differences were found with isometric torque although % changes pre-post in peak power across isokinetic velocities ranging from 30 to 240 degrees were significantly greater with LIT. One repetition max (1RM) increased post-training in all groups with a trend towards increased strength at the mid-assessment for BFR only (p=0.0537). Total reps completed were significantly lower and total training volume higher with HIT. Session RPE was not different among protocols. There were no changes in lower leg lean or fat mass as assessed by DXA. CONCLUSIONS: In general, all three training protocols resulted in increased 1RM strength following five weeks of training with no changes in body composition. Supported by NIH grant UL1 TR00153 and the Undergraduate Research Opportunities Program at UCI.